Footballscience.net
As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.
Following studies were retrieved for this week:
#1 Brain Endurance Training Improves Physical, Cognitive, and Multitasking Performance in Professional Football Players
Reference: Int J Sports Physiol Perform. 2022 Nov 11;1-9. doi: 10.1123/ijspp.2022-0144. Online ahead of print.
Authors: Walter Staiano, Michele Merlini, Marco Romagnoli, Ulrich Kirk, Christopher Ring, Samuele Marcora
Summary: Brain endurance training (BET)-the combination of physical training with mentally fatiguing tasks-could help athletes adapt and increase their performance during sporting competitions. Here we tested whether BET completed after standard physical training improved physical and mental performance more than physical training alone during a preseason football training camp. The study employed a pretest/training/posttest design, with 22 professional football players randomly assigned to BET or a control group. Both groups completed 40 physical training sessions over 4 weeks. At the end of a day of physical training, the BET group completed cognitive training, whereas the control group listened to neutral sounds. Players completed the 30-15 Intermittent Fitness Test, repeated sprint ability random test, soccer-specific reactive agility test, and Stroop and psychomotor vigilance tests pretraining and posttraining. Mixed analysis of variance was used to analyze the data. In the posttest (but not pretest) assessments, the BET group consistently outperformed the control group. Specifically, the BET group was faster (P = .02-.04) than the control group during the 30-15 Intermittent Fitness Test, the directional phase of the repeated sprint ability random test, and the soccer-specific reactive agility test. The BET group also made fewer errors (P = .02) during the soccer-specific reactive agility test than the control group. Finally, the BET group responded faster (P = .02) on the Stroop test and made fewer (P = .03) lapses on the psychomotor vigilance test than the control group. The inclusion of BET during the preseason seems more effective than standard physical training alone in improving the physical, cognitive, and multitasking performance of professional football players.
#2 Association of the CKM rs8111989 Polymorphism with Injury Epidemiology in Football Players
Reference: Int J Sports Med. 2022 Nov 11. doi: 10.1055/a-1945-8982. Online ahead of print.
Authors: David Varillas-Delgado, Esther Morencos, Jorge Gutierrez-Hellín, Millan Aguilar-Navarro, Antonio Maestro, Teresa Perucho, Juan Del Coso
Summary: The influence of the rs8111989 polymorphism in the muscle-specific creatine kinase gene (CKM) on injury incidence is unknown. The aim was to investigate CKM polymorphism on injury incidence in high-performance football players. A cohort of 109 high-performance players was genotyped by using saliva samples. Injury incidence was similar in players with the GG, GA, and AA genotypes and did not modify incidence during training or match exposure (p=0.583 and p=0.737 respectively). GG players had a higher frequency of slight-severity injuries (60.0 vs. 10.2 vs. 24.2%, p<0.001), while GA players had a higher frequency of severe injuries (16.7 vs. 30.8 vs. 10.0%, p=0.021). GA players also had a higher frequency of muscle tears (34.8 vs. 59.0 vs. 20.0%, p<0.001). Muscle contracture was a more frequent injury in players with the GG genotype (40.0%, p<0.001). G allele carriers had lower frequencies of gradual-onset injuries (4.1 vs. 16.7%, p=0.035) and recurrent injuries (6.1 vs. 16.7%, p=0.003) than AA players. A allele carriers had higher frequency of severe injuries (10.0 vs. 21.9%, p=0.044) than GG players. Genotypes in the CKM rs8111989 polymorphism did not affect injury incidence in high-performance football players. Players with the GA genotype were more prone to severe injuries and muscle tears when compared to GG and AA players.
#3 Science and the World Cup: how big data is transforming football
Reference: Nature. 2022 Nov;611(7936):444-446. doi: 10.1038/d41586-022-03698-1.
Authors: David Adam
Download link: https://www.nature.com/articles/d41586-022-03698-1.pdf
#4 Differences in Body Composition Analysis by DEXA, Skinfold and BIA Methods in Young Football Players
Reference: Children (Basel). 2022 Oct 28;9(11):1643. doi: 10.3390/children9111643.
Authors: José Francisco Tornero-Aguilera, Bella Esperanza Villegas-Mora, Vicente Javier Clemente-Suárez
Download link: https://www.mdpi.com/2227-9067/9/11/1643/htm
Summary: The most widely used method in professional sports for fat percentage assessment is the skinfold method. However, there is the chance of bias and human error. For this reason, other more precise methods are used, such as single-frequency bioelectrical impedance analysis (BIA) or dual energy X-ray absorptiometry (DEXA). However, there are limited data that demonstrate the methodological shortcomings or congruences in fat and fat-free mass estimates including gender differences and differences in athlete populations. Thus, the aim of the present study was to compare total body fat (%BF) estimated by six skinfold thickness measurement (SKF) and single-frequency bioelectrical impedance analysis (BIA) methods, using three different sets of equations, to that assessed by the dual energy X-ray absorptiometry (DEXA) method using a DEXA Hologic Serie Discovery QDR. For this aim, 76 males and 70 females belonging to the professional Spanish football federation were evaluated. We found significant differences between the three measures. BIA significantly underestimates the fat percentage, followed by skinfolds. With DEXA being the more objective or accurate method, an equation is established by means of linear regression analysis that allows the percentage of adipose tissue to be obtained either through anthropometry or electrical bioimpedance and adjusted to that which would be obtained by the DEXA system.
#5 Genetic Variations between Youth and Professional Development Phase English Academy Football Players
Reference: Genes (Basel). 2022 Nov 1;13(11):2001. doi: 10.3390/genes13112001.
Authors: Alexander B T McAuley, David C Hughes, Loukia G Tsaprouni, Ian Varley, Bruce Suraci, Joseph Baker, Adam J Herbert, Adam L Kelly
Download link: https://www.mdpi.com/2073-4425/13/11/2001/htm
Summary: The purpose of this study was to examine differences in the genotype frequency distribution of thirty-three single nucleotide variants (SNVs) between youth development phase (YDP) and professional development phase (PDP) academy football players. One hundred and sixty-six male football players from two Category 1 and Category 3 English academies were examined within their specific age phase: YDP (n = 92; aged 13.84 ± 1.63 years) and PDP (n = 74; aged 18.09 ± 1.51 years). Fisher's exact tests were used to compare individual genotype frequencies, whereas unweighted and weighted total genotype scores (TGS; TWGS) were computed to assess differences in polygenic profiles. In isolation, the IL6 (rs1800795) G allele was overrepresented in PDP players (90.5%) compared to YDP players (77.2%; p = 0.023), whereby PDP players had nearly three times the odds of possessing a G allele (OR = 2.83, 95% CI: 1.13-7.09). The TGS (p = 0.001) and TWGS (p < 0.001) were significant, but poor, in distinguishing YDP and PDP players (AUC = 0.643-0.694), with PDP players exhibiting an overall more power-orientated polygenic profile. If validated in larger independent youth football cohorts, these findings may have important implications for future studies examining genetic associations in youth football.
#6 Effect of playing position and microcycle days on the acceleration speed profile of elite football players
Reference: Sci Rep. 2022 Nov 10;12(1):19266. doi: 10.1038/s41598-022-23790-w.
Authors: Antonio Alonso-Callejo, Jorge García-Unanue, Andrés Perez-Guerra, David Gomez, Javier Sánchez-Sánchez, Leonor Gallardo, Jose María Oliva-Lozano, Jose Luis Felipe
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9649751/pdf/41598_2022_Article_23790.pdf
Summary: The aim of this study was to analyse the differences in the A-S profile of elite football players induced by playing position and the microcycle day. Players belonged to a second division club in the Spanish La Liga competition. They were classified into five playing positions: central defenders (CD), full backs (FB), midfielders (MF), wide midfielders (WMF) and forwards (FW). Microcycle days were categorised according to the days until matchday (MD, MD-1, MD-2, MD-3, MD-4 and MD-5). Data was collected along six microcycles, including one match per microcycle. The variables analysed were: maximal theoretical acceleration (A0), maximal theoretical speed (S0), maximal acceleration (ACCmax), maximal speed (Smax) and A-S slope (ASslope). Significant differences were found within positions and microcycle day for all variables (p < 0.05). Match day (MD) showed greater values than the training sessions in A0, ACCmax and Smax (p < 0.05). The highest values for variables associated with acceleration capabilities were found in CD on MD, whereas speed variables were higher in WMF. MD-2 showed the lowest values in all variables except for ASslope. Maximal acceleration and sprint abilities are therefore affected by playing position. Wide positions showed the highest speed capacity, and CD presented a likely acceleration profile. Higher values for all variables concerning the microcycle day, were achieved on MD, and were not reproduced during training with the consequent injury risk and performance decrease it takes.
#7 The Effects of a Weighted Football Intervention on Ball Velocity of a Standard Football Place-Kick among Elite Gaelic Football Goalkeepers: A Single-Subject Designed Study
Reference: Sports (Basel). 2022 Oct 28;10(11):166. doi: 10.3390/sports10110166.
Authors: Sam Jermyn, Cian O'Neill, Seán Lacey, Edward K Coughlan
Download link: https://www.mdpi.com/2075-4663/10/11/166/htm
Summary: Weighted football place-kicking acutely enhances the ball velocity (BV) of subsequent standard football place-kicks. However, there is a dearth of research examining the long-term effects of such interventions, with less evidence in existence among elite athlete cohorts. Therefore, the purpose of this study was to investigate the individual effects of a 4 week, eight-session weighted Gaelic football intervention on BV of standard Gaelic football place-kicks among six elite male Gaelic football goalkeepers. This research design was based on a pre-, mid-, post-, and retention-test design. A linear mixed model analysis was employed, with time and participants as fixed effects, and the number of place-kicks per testing session as a random effect. Post hoc tests revealed significant changes in BV for five of the six participants (p < 0.05), with three participants experiencing significant BV increases from pre-test to post-test (p < 0.05), while no significant differences were found between post-test and retention-test. The remaining three participants experienced no significant BV differences from pre-test to post-test and retention-test. These findings suggest that a weighted football place-kicking intervention can be a time-efficient means of maintaining and enhancing BV and, thus, kick distance, among elite goalkeepers during pre-season and in-season phases.
#8 The prevalence and determinants of anterior cruciate ligament rupture among athletes practicing football in Jeddah Avenues 2020
Reference: J Family Med Prim Care. 2022 Aug;11(8):4528-4535. doi: 10.4103/jfmpc.jfmpc_61_22. Epub 2022 Aug 30.
Authors: Fahad Salem Alqarni, Khalid Omair Alshehri, Turki Muteb Alotaibi, Assaf Nahar Alsulami, Abdulaziz Omair Alshehri, Khaled Saeed Aseri
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9638634/pdf/JFMPC-11-4528.pdf
Summary: Anterior cruciate ligament (ACL) tear is a common sport injury and one of the most serious sport injuries affecting non-professionals and professional athletes. It is most commonly torn during sports that involve sudden stops and changes in direction such as football. The aim was too measure the prevalence and determinants of anterior cruciate ligament rupture as well as assess knowledge about it among young adult athletes practicing football. An analytical cross-sectional study based on a questionnaire was carried out during the period from December 2019 to March 2020 among a sample of Saudi athletes recruited from natural grass, artificial turf, and dirt football fields in the Jeddah region. A structured questionnaire composed of four parts was used to collect data: socio-demographic variables, questions to assess awareness and knowledge of ACL, questions to assess the prevalence and determinants of ACL, and description of cases and the Arabic version of the Lysholm Knee Score (LKS) to assess the impact of ACL injury on patients' daily life. The study included 320 participants. Their age ranged between 15 and 40 years with an arithmetic mean of 27.9 and a standard deviation of ±6.8 years. The majority of them were males (97.8%). The prevalence of ACL injury was 14.7% among the participants; it was significantly higher among overweight and obese subjects (P = 0.042) as well as those who reported more than 10 training weekly hours (P = 0.034). Most of the playgrounds at the time of injury were either artificial turf (44.7%) or dirt football fields (34%). Overall, the level of adequate knowledge about ACL was observed among most of the participants (70.3%). The only factor significantly associated with the level of participants' knowledge about ACL was the level of physical activity, P = 0.011. The total of LKS ranged between 21 and 100 with a median (inter-quartile range) of 82.5 (57-91). The prevalence rate of ACL injury among athletes in Jeddah, Saudi Arabia, is within the world wide range. Their awareness and knowledge of ACL are encouraging, although some risk factors were not well known. The quality of life of injured athletes was high, irrespective of demographic as well as physical factors and the history of surgical repair.
#9 Immediate Effects of Spinal Manipulative Therapy on the Performance of Elite Brazilian Soccer Players: A Pilot Randomized Controlled Trial With an Internally Validated Sham Treatment
Reference: J Chiropr Med. 2022 Dec;21(4):270-279. doi: 10.1016/j.jcm.2022.02.021. Epub 2022 Jul 15.
Authors: Marcelo B Botelho, Marcio A Barbosa, Celso S Junior, Jerusa P R Lara, Alexandre Moreira, Abrahão F Baptista
Summary: The purpose of this study was to assess the feasibility of the procedures' routine, the recruiting rate, the presence of any significant detrimental impact on the players' training routine, and the sham efficacy in achieving blinding. A parallel randomized controlled clinical trial was performed with 20 elite soccer players who were randomly assigned to 1 of 2 groups: spinal manipulative therapy (SMT) and sham SMT. All players were from the same team, were injury free, and were naive to SMT. Measured outcome tests (30-m sprint run with a 10-m split and change of direction [COD] test) were performed at the same time by all participants immediately before and after interventions. Photocell devices were used for data acquisition. Twenty participants were analyzed (10 in each group). There were no changes to the sprint (10 m and 30 m) and COD test results immediately after either of the interventions. All participants in both groups (SMT and sham SMT) answered "yes" to a question after the intervention asking if they were treated by SMT. No adverse effects or training routine impairment were reported. This pilot study protocol showed it was an appropriate design for a confirmatory clinical trial. The study had minimal effect on the team training routine, and the recruitment rate was excellent. The proposed sham SMT strategy was successful in blinding the players. In this sample, SMT did not have any immediate effect on the performance of these elite soccer players, as measured by 10- and 30-m sprint times and COD sprint times.
#10 Match activity profile of professional female soccer players during a season
Reference: J Exerc Rehabil. 2022 Oct 26;18(5):324-329. doi: 10.12965/jer.2244354.177. eCollection 2022 Oct.
Authors: Jun-Hyuk Choi, Chang-Hwa Joo
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9650312/pdf/jer-18-5-324.pdf
Summary: It is necessary to understand movement characteristics of elite female soccer players during a match to develop effective training program. The purpose of this study is to analyze the physical demands of Korean female professional soccer players during a competitive season. Twenty-four female professional players (age: 27.8±3.9 years; height: 165.7± 5.1 cm) from a team, belonging to the women's professional soccer league in South Korea participated in the study. The players participated in 11 home matches and 10 away matches from April 26 to November 9 of the 2011 season. Body weight and body mass index decreased during the first half-season compared to the preseason (P<0.05), and the decreased values were maintained until the second half-season. Total distance covered by the players was more than 9.5 km per match. No difference was found in the total distance, movement distance by exercise intensities, number of sprints and accelerations, and maximum speed between the first half- and second half-seasons. Midfielders covered the most distance during a match compared to other positions (P<0.05). Wing forward covered the most distance of high-intensity exercise. Maximum speed during the match was higher among wing forward and forward than in other positions (P<0.05). There were no significant differences between home and away matches in all variables (P>0.05). In conclusion, in order to improve the performance of female soccer players and prevent injuries, a training program should be constructed that considers the characteristics of each player and playing position rather than uniform training in a team.
#11 Men Are from Quartile One, Women Are from? Relative Age Effect in European Soccer and the Influence of Age, Success, and Playing Status
Reference: Children (Basel). 2022 Nov 14;9(11):1747. doi: 10.3390/children9111747.
Authors: Matthew Andrew, Laura Finnegan, Naomi Datson, James H Dugdale
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9689054/pdf/children-09-01747.pdf
Summary: The relative age effect (RAE) is characterised by an overrepresentation of athletes born earlier in the selection year. Whilst an RAE is consistently evident in male soccer, examinations in female players remain limited. The aim of the present study was to examine the influence of sex, as well as age, success, and playing status in European soccer players. The sample consisted of a total of 6546 soccer players from 55 soccer nations that competed in recent European Championship qualification campaigns. Results indicated an evident RAE in male [p = 0.017] but not female [p = 0.765] players. Male players were over-represented by players born in the first quartile for the U17 [p < 0.001] and U19 [p = 0.001] levels, however, this over-representation did not transfer to senior levels. No RAE was observed at any level for female players. Inside each age group, a slight selection bias towards those born in the first quartile for successful squads was observed but did not significantly differentiate between qualification status for either male or female players. Results from this study highlight the disparity in RAE prevalence between male and female players and raise further questions regarding the value of selecting relatively older players to metrics of success, transition, and selection for senior international soccer.
#12 Recreational Soccer Training Effects on Pediatric Populations Physical Fitness and Health: A Systematic Review
Reference: Children (Basel). 2022 Nov 18;9(11):1776. doi: 10.3390/children9111776.
Authors: Filipe Manuel Clemente, Jason Moran, Rodrigo Ramirez-Campillo, Rafael Oliveira, João Brito, Ana Filipa Silva, Georgian Badicu, Gibson Praça, Hugo Sarmento
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9689246/pdf/children-09-01776.pdf
Summary: This systematic review analyzed the effects of recreational soccer programs on physical fitness and health-related outcomes in youth populations. Studies were sought in the following databases: (i) PubMed, (ii) Scopus, (iii) SPORTDiscus, and (iv) Web of Science. The eligibility criteria included (1) population: youth (<18 years old) populations with no restrictions on sex or health condition; (2) intervention: exposure to a recreational soccer training program of at least four weeks duration; (3) comparator: a passive or active control group not exposed to a recreational soccer training program; (4) outcomes: physical fitness (e.g., aerobic, strength, speed, and change-of-direction) or health-related measures (e.g., body composition, blood pressure, heart rate variability, and biomarkers); (5) study design: a randomized parallel group design. The search was conducted on 6 September 2022 with no restrictions as to date or language. The risk of bias was assessed using the PEDro scale for randomized controlled studies. From a pool of 37,235 potentially relevant articles, 17 were eligible for inclusion in this review. Most of the experimental studies revealed the beneficial effects of recreational soccer for improving aerobic fitness and its benefits in terms of blood pressure and heart-rate markers. However, body composition was not significantly improved by recreational soccer. The main results revealed that recreational soccer training programs that are implemented twice a week could improve the generality of physical fitness parameters and beneficially impact cardiovascular health and biomarkers. Thus, recreational soccer meets the conditions for being included in the physical education curriculum as a good strategy for the benefit of the general health of children and young people.
#13 Physical Fitness Variations between Those Playing More and Those Playing Less Time in the Matches: A Case-Control Study in Youth Soccer Players
Reference: Children (Basel). 2022 Nov 21;9(11):1786. doi: 10.3390/children9111786.
Authors: Ana Filipa Silva, Filipe Manuel Clemente, César Leão, Rafael Oliveira, Georgian Badicu, Hadi Nobari, Luca Poli, Roberto Carvutto, Gianpiero Greco, Francesco Fischetti, Stefania Cataldi
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9689158/pdf/children-09-01786.pdf
Summary: The purpose of this study was (i) to compare two groups (players with more vs. less match play time) regarding body composition, vertical and horizontal jumping performance, and aerobic capacity; and (ii) to test the relationships between physical fitness and play time. This study followed a case-control design in which the outcome was playtime, and the causal attribute was physical fitness. Sixty-six youth male soccer players from under-16 (n = 21), under-17 (n = 19), under-18 (n = 12), and under-19 (n = 14) age groups were monitored for match play time during five months of observation. Inclusion criteria consisted of (1) no absence of more than a week due to injury or other conditions during the five months of observation and (2) physical assessments having been done simultaneously with those of the other players (at the beginning of the season). The exclusion criteria were (1) not participating in one week or more of training sessions, and (2) not participating in the physical fitness assessments. At the beginning of the season, players were assessed for anthropometry (height, body mass, skinfolds), countermovement jump, triple hop bilateral and unilateral jump, and aerobic capacity using the Yo-Yo Intermittent Recovery Test, level 2 (YYIRT). The group that played more time had significantly greater YYIRT results (+28.2%; p = 0.009; Cohen's d = 0.664). No other significant differences were found between those who played more and fewer minutes. Moderate and significant linear positive correlations were found between YYIRT and play time in the under-19 group (r = 0.423; p = 0.031) and overall (r = 0.401; p < 0.001). In the case of the under-17 group, moderate and significant linear positive correlations were found between TSA and play time (r = 0.473; p = 0.041). This suggests that aerobic and anaerobic capacity is related to play time while jumping performance and fat mass seem not to play an essential role in play time.
#14 Analysis of the Anaerobic Power Output, Dynamic Stability, Lower Limb Strength, and Power of Elite Soccer Players Based on Their Field Position
Reference: Healthcare (Basel). 2022 Nov 10;10(11):2256. doi: 10.3390/healthcare10112256.
Authors: Ali AlTaweel, Shibili Nuhmani, Mohammad Ahsan, Wafa Hashem Al Muslem, Turki Abualait, Qassim Ibrahim Muaidi
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9690877/pdf/healthcare-10-02256.pdf
Summary: Soccer players require a high degree of aerobic and anaerobic fitness to perform well throughout the game as per their position in the field. This study aimed to investigate the differences in anaerobic power output, dynamic stability, lower limb strength, and power among elite soccer players based on their field position. A cross-sectional population of 96 elite soccer players with average age 23.10 ± 4.35 years, weight 69.99 ± 9.71 kg, height 174.84 ± 6.64 cm, and body mass index 22.84 ± 2.39 kg/m2 from various soccer clubs in Saudi Arabia was tested for their anaerobic power output, dynamic stability, lower limb strength, and power performance. All the participants have more than 4 years of experience in competitive soccer events. Tests included a measure of single-leg vertical jump, star excursion balance test, and single-leg triple hop test for distance. The players were divided into four groups (goalkeepers, defenders, midfielders, and attackers) based on their self-reported position on the field. One-way ANOVA was used to determine the differences between all variables according to the players' position. In addition, partial eta-squared (ηp2) was used to report effect sizes. The results revealed significant differences between positions in the anaerobic power output (p = 0.012, ηp2 = 0.312), dynamic stability {Anterior (p = 0.004, ηp2 = 0.235), Anteromedial (p = 0.007, ηp2 = 0.622), Anterolateral (p = 0.011, ηp2 = 0.114)}, and lower limb strength, and power (p = 0.008, ηp2 = 0.421). At the same time, goalkeepers' performance was significantly superior to midfielders (p = 0.006) in the anaerobic power output. In addition, lower limb strength and power was significantly higher (p = 0.004) for goalkeepers than for midfielders, with a similar trend in dynamic stability (p = 0.007). These results exhibited differences in anaerobic power output, dynamic stability, lower limb strength, and power performance based on the players' positions. The investigation may assist the practitioner in designing training programs for the players according to their position for performance improvement.
#15 Muscle Asymmetries in the Lower Limbs of Male Soccer Players: Preliminary Findings on the Association between Countermovement Jump and Tensiomyography
Reference: Sports (Basel). 2022 Nov 14;10(11):177. doi: 10.3390/sports10110177.
Authors: Alex Buoite Stella, Annalisa Galimi, Miriam Martini, Luca Di Lenarda, Luigi Murena, Manuela Deodato
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9694285/pdf/sports-10-00177.pdf
Summary: Strength and power asymmetries have been observed in different sports, including soccer. Such asymmetries, as well as the bilateral deficit (BLD), can be assessed during different tasks, static or dynamic, and with different methods and devices, in order to detect the possible different aspects, as well as the association with physical performance and injuries. The aim of this study was to investigate the association between muscle asymmetries and BLD during a countermovement jump (CMJ), and tensiomyography (TMG) parameters and asymmetries, in the lower limbs of male soccer players. A total of 23 male soccer players (18 ± 4 years) were recruited. Bilateral and unilateral CMJs were performed, and peak power (W) and height (cm) were obtained. TMG was performed on different muscles of the lower limbs, and lateral and functional symmetries were obtained. Playing position and history of injuries were collected. CMJ inter-limb symmetry was found to significantly correlate with biceps femoris (r = 0.574, p = 0.004) and soleus (r = 0.437, p = 0.037) lateral symmetry. Players in central roles presented significantly worse functional symmetry scores of the knee than defense players (-17.5%, 95% CI -31.2--3.9; p = 0.10). Participants reporting a history of injury at the ankle were characterized by significantly lower functional symmetry in both the dominant (43%, 39.5-48.0 vs. 74.5%, 46.5-89.3, p = 0.019) and non-dominant (45%, 42.5-46.0 vs. 81.0%, 45.8-90.3, p = 0.024) ankle. Findings from this preliminary study suggest an association between lower-limb muscle asymmetries during a dynamic task, such as jumping, and muscle contractile properties evaluated with TMG; moreover, functional asymmetries may be present after ankle injuries. Future studies in larger samples should evaluate the presence of such asymmetries as predictors or characteristics of different muscular and joint injuries.
#16 Effects of Age and Playing Tactics on the Individual Tactical Behavior in U10 and U12 Elite Spanish Soccer Players
Reference: Sports (Basel). 2022 Nov 21;10(11):185. doi: 10.3390/sports10110185.
Authors: Joaquín González-Rodenas, Gonzalo Pedrera, Víctor Dorado, Rodrigo Aranda-Malavés, Andrés Tudela-Desantes, Pedro De Matías-Cid
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9693199/pdf/sports-10-00185.pdf
Summary: The aim of this paper was to explore the effects of age and playing tactics on the individual tactical behavior and performance in young soccer players. A total of 1247 individual possessions during 16 knockout matches from LaLiga Promises U12 tournament (n = 621) and LaLiga U10 Iscar Cup (n = 626) were analyzed by observational methodology. Multilevel and multivariate logistic regression models were created to explain the interdependent effects of age category and playing tactics on the individual tactical behavior and performance. Youth players performed most of their actions against defensive pressure (72.5%), during offensive support (91.3%) and receiving the ball facing forward (62.6%). The most frequent action was to receive and pass the ball (69.6%) and the level of offensive success was 56.9%. The multilevel mixed models revealed that U10 players presented higher odds of running with the ball vs. passing the ball (OR = 1.823; 95% CI: 1.333-2.493; p < 0.001) and lower odds of achieving offensive success (OR = 0.698; 95% CI: 0.525-0.928; p < 0.05) than U12 players. Regarding playing tactics, technical-tactical dimensions such as the players' body shape when receiving the ball, offensive support, defensive pressure, collective type of attack and type of technical action presented a significant and combined effect on the offensive success regardless of age category, playing position and match status. This study found tactical differences between U10 and U12 age categories and revealed important interactive effects of multiple tactical dimensions on the individual offensive behavior and performance in youth soccer players.
#17 Testing the effects of 4-week training programs based on extreme and medium-sided soccer games: a study focusing on change-of-direction, vertical jump height and locomotor profile
Reference: BMC Sports Sci Med Rehabil. 2022 Nov 24;14(1):199. doi: 10.1186/s13102-022-00592-1.
Authors: Piotr Makar, Gibson Praça, Adam Kawczyński, Zeki Akyildiz, Mehmet Yıldız, Rodrigo Aquino, Filipe Manuel Clemente
Download link: https://bmcsportsscimedrehabil.biomedcentral.com/counter/pdf/10.1186/s13102-022-00592-1.pdf
Summary: This study tested the effects of two training programs (one program based on extreme sided-games of 1v1 vs. one program based on the medium-sided game of 5v5) on the physical fitness adaptations of youth soccer players. In specific, it was analyzed the effects of the training programs on the 5-0-5 change-of-direction time (5-0-5 time), countermovement jump (CMJ), and final velocity in the 30-15 Intermittent Fitness test (VIFT). This study followed a randomized parallel study design. Twenty male regional-level soccer players (age: 17.0 ± 0.3 years old) were randomly assigned to two groups: (1) the 1v1 format; and (2) the 5v5 format. The training intervention lasted four weeks. The week before (baseline) and the week after the intervention, the participants were assessed in the 5-0-5 change-of-direction test (measured using timing gates), CMJ (measured by photoelectric cells), and 30-15 Intermittent Fitness test. The training intervention consisted of 8 sessions (2 sessions per week). The 1v1 group performed four repetitions of 30 s in each session, while the 5v5 group performed four repetitions of 4 min. The 5-0-5 time changed - 4.82% (p = 0.004; d = 1.115) for the 1v1 group and - 4.26% (p = 0.004; d = 0.859) for the 5v5 group. CMJ changes occurred both in the 1v1 and 5v5 group and amounted to 1.7% (p = 0.003; d = 0.509) and 1.2% (p = 0.263; d = 0.155) respectively. VIFT changed 2.6% (p = 0.718; d = 0.178) for the 1v1 group and 3.0% (p = 0.593; d = 0.274) for the 5v5 group. The 1v1 group reported significantly lower post-intervention 5-0-5 time than the 5v5 group (- 4.3%; p = 0.048; d = 0.954), although no significant differences in CMJ (3.2%; p = 0.147; d = 0.678) and VIFT (2.5%; p = 0.697; d = 0.177) were revealed. The extreme-sided games meaningfully beneficiated the vertical jump height and change-of-direction performance of youth soccer players. The extreme-sided games seem more beneficial than medium-sided games for improving these physical abilities while showing that four weeks were enough to impact the players significantly.
#18 Daytime fluctuations of endurance performance in young soccer players: a randomized cross-over trial
Reference: BMC Res Notes. 2022 Nov 24;15(1):351. doi: 10.1186/s13104-022-06247-1.
Authors: Janis Fiedler, Stefan Altmann, Hamdi Chtourou, Florian A Engel, Rainer Neumann, Alexander Woll
Download link: https://bmcresnotes.biomedcentral.com/counter/pdf/10.1186/s13104-022-06247-1.pdf
Summary: Fluctuations of physical performance and biological responses during a repetitive daily 24-h cycle are known as circadian rhythms. These circadian rhythms can influence the optimal time of day for endurance performance and related parameters which can be crucial in a variety of sports disciplines. The current study aimed to evaluate the daytime variations in endurance running performance in a 3.000-m field run and endurance running performance, blood lactate levels, and heart rate in an incremental treadmill test in adolescent soccer players. In this study, 15 adolescent male soccer players (age: 18.0 ± 0.6 years) performed a 3.000-m run and an incremental treadmill test at 7:00-8:00 a.m. and 7:00-8:00 p.m. in a randomized cross-over manner. No significant variations after a Bonferroni correction were evident in endurance running performance, perceived exertion, blood lactate levels, and heart rates between the morning and the evening. Here, the largest effect size was observed for maximal blood lactate concentration (9.15 ± 2.18 mmol/l vs. 10.64 ± 2.30 mmol/l, p = .110, ES = 0.67). Therefore, endurance running performance and physiological responses during a field-based 3.000-m run and a laboratory-based test in young male soccer players indicated no evidence for daytime variations.
